In order to meet the wireless data traffic demand that is on an increasing trend after commercialization of 4G communication system, efforts for developing improved 5G communication system or pre-5G communication system have been made. For this reason, the 5G communication system or pre-5G communication system has been called beyond 4G network communication system or post LTE system.
In order to achieve high data rate, implementation of 5G communication system in a millimeter Wave (mmWave) band (e.g., like 60 GHz band) has been considered. In order to mitigate a radio wave path loss and to increase a radio wave transmission distance in the mmWave band, technologies of beam-forming, massive MIMO, Full Dimension MIMO (FD-MIMO), analog beam-forming, and large scale antenna for the 5G communication system have been discussed.
Further, for system network improvement in the 5G communication system, technology developments have been made for an evolved small call, advanced small cell, cloud Radio Access Network (cloud RAN), ultra-dense network, Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and reception interference cancellation.
In addition, Hybrid FSK and QAM Modulation (FQAM) and Sliding Window Superposition Coding (SWSC), which correspond to Advanced Coding Modulation (ACM) system, and Filter Bank Multi Carrier (FBMC), Non-Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access SCMA), which correspond to advanced connection technology, have been developed in the 5G system.
In general, a mobile communication system was developed for the purpose of providing a voice service while securing user's mobility. However, the area of the mobile communication system has been expanded gradually to data services in addition to voice services, and, at present, the mobile communication system has been developed to the extent of being capable of providing high-speed data services. However, in the mobile communication system that is currently providing a high-speed data service, since resources are short, there has been a need for a greatly developed mobile communication system.
On the other hand, unlike a voice service, resources that can be allocated for a data service are determined in accordance with the amount of data to be transmitted and a channel situation. Accordingly, in a wireless communication system, such as a mobile communication system, a scheduler manages allocation of transmission resources in consideration of the amount of resources to be transmitted, the channel situation, and the amount of data. Such management is performed in the same manner even in a Long-Term Evolution (LTE) that is one of the next-generation mobile communication systems, and in this case, the scheduler that is located in a base station manages and allocates wireless transmission resources.
Since an LTE communication system is a system that uses licensed frequencies, it can exclusively use frequency resources through a method that is desired by an owner. However, in the case of unlicensed frequencies, several communication devices can non-exclusively share and use frequency resources. The frequency resources that are allocated to communication service providers are limitative, and in spite of the development of high technology in accordance with an abrupt increase of traffic, medium/long-term frequency demands from the communication service providers have been increased. In addition, since the frequency demand scale in the fields of broadcasting, public, and misfortune services excluding communications is on an increasing trend, it gets difficult to flexibly cope with the demand-supply relations of such various frequency resources through an exclusive frequency distribution method based on the licensing method. Accordingly, even in the LTE communication system, LTE-Unlicensed (LTE-U) technology has been developed to provide services using unlicensed frequencies. Accordingly, there is a need for discussion of cell selection and switching methods through a base station in the non-licensed frequency band.
However, since the existing cell selection and switching methods in the non-licensed band are performed on the basis of long-term channel measurement information that corresponds to several seconds or several hours, a relatively long delay occurs in changes. Further, channel occupation becomes unreliable due to the unlicensed band characteristics with respect to a corresponding frequency channel after the channel change. Since various Radio Access Technologies (RAT), such as WiFi and LTE-U, competitively occupy the channel resources in the corresponding unlicensed band and use separate communication protocols and control signaling, there exist limitations in sharing information about channel occupation or interference situations of neighboring links.
Accordingly, in the case where a user terminal uses only determined unlicensed band channels, channel occupation according to peripheral transmission is limited. Accordingly, User Perspective Throughput (UPT) is deteriorated, and transmission delay is increased to cause limitations in performance.